Common rail fuel systems typically include a fuel source and fuel delivery components for supplying fuel directly into cylinders of an internal combustion engine by way of a common rail. Fuel within the common rail may be pressurized to a relatively high pressure using one or more pumps, and may be delivered to fuel injectors through a plurality of individual fuel supply passages. A control system may be associated with the fuel system to monitor and control operation of one or more of the fuel system components. Specifically, for example, the control system may be configured to control the high-pressure pump and each of the fuel injectors to control pressurization rates and injection, thus improving performance and control of the engine. Typically, such fuel systems also include some means to protect the system against gross over-pressurization, which may occur due to one or more of an operational, control, or component problem. Often, this protection is provided through the use of a pressure relief valve, which may be mechanically or electronically actuated when rail pressure is above a predetermined maximum operating pressure.
Engineers are constantly seeking improved performance and expanded capabilities for such fuel systems. For example, a low static leak fuel system may provide minimal leakage and, as a result, may improve the overall efficiency, reliability, and durability of common rail fuel systems. However, the lack of static leakage from the fuel system may present a previously unrecognized performance challenge, such that when a reduction in rail pressure is required, the pressure may not be reduced at a desired rate. More specifically, conventionally designed fuel systems, which may allow a tolerable amount of leakage, may increase a reduction rate, or decay rate, of pressure within the rail, whereas the low static leak fuel system may not. As a result, for example, the settle time required for an operational engine having a low static leak fuel system to go from a high load condition, during which relatively high rail pressures are used, to a low load or idle condition, during which relatively low rail pressures are used, may be compromised.
As introduced above, a variety of mechanical and electronic means for preventing over-pressurization within common rail fuel systems are generally known. For example, U.S. Pat. No. 7,392,792 teaches a pressure relief valve that may fluidly connect the common rail to the fuel tank via a fluid passageway to relieve pressure from the fuel system. Although the commonly owned reference is directed to a method for dynamically detecting fuel leakage, a pressure relief valve that may be actuated when rail pressure exceeds a biasing spring force and/or when a solenoid is energized is described. While the reference may effectively reduce or prevent over-pressurization from occurring, it does not recognize a need for controlling rail pressure in low static leak fuel systems.
The present disclosure is directed to one or more of the problems set forth above.